Aluminum die castings and steels are generally used as materials for each member of a tread and a riser that constitute a tread unit of a passenger conveyor such as an escalator. In recent years, tread units using fiber reinforced plastic (FRP) have also been proposed.
FIG. 13 shows a conventional tread unit of an escalator disclosed in Japanese Patent Application Laid-open No. Hei 7-330266, and FIG. 14 shows a tread unit of an escalator disclosed in WO 95/23758 using fiber reinforced plastic. In FIG. 13, reference numeral 101 denotes a tread, 102 denotes a reinforcing rib, 103 denotes a riser, and 106 denotes a bracket. This tread unit is made solely of aluminum die castings. Further, in FIG. 14, reference numerals 102a and 102b denote reinforcing ribs. This tread unit is made solely of fiber reinforced plastic.
Also, in Japanese Utility Model Application Laid-open No. Hei 6-8372, a sectional view of a tread of a passenger conveyor is shown and it discloses that the surface of the tread is provided with a film made of quartz sand thereby facilitating and reducing costs of non-slip processing. Further, in Japanese Patent Application Laid-open No. Sho 63-139808, it is disclosed that steel wires and rubber belts reinforced by woven fabrics are used as a conveying body.
As described above, most of the conventional tread units of passenger conveyors such as escalators are made of aluminum die castings, with some made of steel. In the case of using aluminum die castings, reinforcing members made of steel are arranged at the lower portion of the tread in order to ensure a prescribed rigidity. Accordingly, weight of the tread unit is increased, and from this arises problems such that the size of the escalator drive unit and the braking force are increased. Furthermore, conventional tread units have another problem in regards to the wear resistance treatment given to the surface of their treads. Since the surface of aluminum die castings provides only poor bond, flaking results, and this leads to defects in reliability and the aesthetic design of the tread unit. Further, in the fiber reinforced plastic proposed in FIG. 14, since short fibers that are several centimeters long or so are used as reinforcement, rigidity and strength are not adequate, and thus an extremely complicated reinforcing rib structure is required at the lower portion of the tread. From this arises still other problems in that structural defects easily occur due to poor wetting of resins, nonuniform distribution of reinforcement and the inclusion of voids and the like during the molding process at the time of manufacture, and the weight of the unit is increased. Also, these problems have caused increased production costs as well. Further, for conveyor belts used for conveying people, the cleats of the tread are only made of rubber, and thus their rigidity is low. As a result, people do not ride stably on such belts.
The present invention has been made to overcome the aforementioned problems. Therefore, an object of the present invention is to obtain a tread unit made of fiber reinforced plastics (hereinafter referred to as an "FRP tread unit") and a passenger conveyor system using such an FRP tread unit, which ensures adequate rigidity and strength using reinforcements made of continuous long fibers, which allows a highly reliable surface treatment to be given, and in which diversified aesthetic designs and reductions in weight can be implemented.